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DOI	10.5194/acp-19-1703-2019
	Evidence for a major missing source in the global chloromethane budget from stable carbon isotopes
	Bahlmann E.; Keppler F.; Wittmer J.; Greule M.; Schöler H.F.; Seifert R.; Zetzsch C.
发表日期	2019
ISSN	16807316
起始页码	1703
结束页码	1719
卷号	19 期号:3
英文摘要	Chloromethane (CH 3 Cl) is the most important natural input of reactive chlorine to the stratosphere, contributing about 16 % to stratospheric ozone depletion. Due to the phase-out of anthropogenic emissions of chlorofluorocarbons, CH 3 Cl will largely control future levels of stratospheric chlorine. The tropical rainforest is commonly assumed to be the strongest single CH 3 Cl source, contributing over half of the global annual emissions of about 4000 to 5000 Gg (1 Gg Combining double low line 109 g). This source shows a characteristic carbon isotope fingerprint, making isotopic investigations a promising tool for improving its atmospheric budget. Applying carbon isotopes to better constrain the atmospheric budget of CH 3 Cl requires sound information on the kinetic isotope effects for the main sink processes: the reaction with OH and Cl in the troposphere. We conducted photochemical CH 3 Cl degradation experiments in a 3500 dm 3 smog chamber to determine the carbon isotope effect (ϵ = k 13 C=k 12 C-1) for the reaction of CH 3 Cl with OH and Cl. For the reaction of CH 3 Cl with OH, we determined an value of (-11:2 ± 0:8)(n = 3) and for the reaction with Cl we found an value of (-10:2 ± 0:5)(n = 1), which is 5 to 6 times smaller than previously reported. Our smaller isotope effects are strongly supported by the lack of any significant seasonal covariation in previously reported tropospheric δ 13 C.CH 3 Cl/values with the OH-driven seasonal cycle in tropospheric mixing ratios. Applying these new values for the carbon isotope effect to the global CH 3 Cl budget using a simple two hemispheric box model, we derive a tropical rainforest CH 3 Cl source of (670 ± 200) Gg a -1 , which is considerably smaller than previous estimates. A revision of previous bottom-up estimates, using above-ground biomass instead of rainforest area, strongly supports this lower estimate. Finally, our results suggest a large unknown CH 3 Cl source of (1530 ± 200) Gg a -1 © 2019 Author(s).
语种	英语
scopus关键词	atmospheric sink; carbon isotope; chlorine; mixing ratio; rainforest; seasonal variation; troposphere
来源期刊	Atmospheric Chemistry and Physics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/144657
作者单位	Institute of Geology, University Hamburg, Bundesstrasse 55, Hamburg, 20146, Germany; Leibniz Centre for Tropical Marine Research, Fahrenheitstraße 6, Bremen, 28359, Germany; Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 234-236, Heidelberg, 69120, Germany; Heidelberg Center for the Environment (HCE), Heidelberg University, Heidelberg, 69120, Germany; Max-Planck-Institute for Chemistry, Hahn-Meitner-Weg 1, Mainz, 55128, Germany; Atmospheric Chemistry Research Unit, BayCEER, University of Bayreuth, Dr Hans-Frisch Strasse 1-3, Bayreuth, 95448, Germany; Agilent Technologies Sales and Services GmbH and Co. KG, Hewlett-Packard-Str. 8, Waldbronn, 76337, Germany
推荐引用方式 GB/T 7714	Bahlmann E.,Keppler F.,Wittmer J.,et al. Evidence for a major missing source in the global chloromethane budget from stable carbon isotopes[J],2019,19(3).
APA	Bahlmann E..,Keppler F..,Wittmer J..,Greule M..,Schöler H.F..,...&Zetzsch C..(2019).Evidence for a major missing source in the global chloromethane budget from stable carbon isotopes.Atmospheric Chemistry and Physics,19(3).
MLA	Bahlmann E.,et al."Evidence for a major missing source in the global chloromethane budget from stable carbon isotopes".Atmospheric Chemistry and Physics 19.3(2019).